1. Field of the Invention
The present invention relates to a disk cartridge for accommodating a disk-shaped information recording medium, used for an information storage device such as a data file device and an image file device, and a method for constructing the same.
2. Description of the Related Art
A write once read many type or rewritable type optical disk is generally accommodated in a cartridge for protection against dust. Such a conventional cartridge is exemplified in Japanese Laid-Open (Kokai) Patent Publication No. 61-236083 (U.S. Pat. No. 4,680,662), which will be shown with reference to FIGS. 14 and 15.
As shown in FIG. 14, the cartridge includes a cartridge box 52 for rotatably accommodating a disk 51. The cartridge box 52 is formed into a substantially rectangular shape consisting of an upper half 53a and a lower half 53b. The upper and lower halves 53a and 53b are provided with center holes 54a, 54b (see FIG. 15) for receiving a disk motor, head slits 55a, 55b (see FIG. 15) for receiving a head, and concave portions 56a. 56b opposing to each other. The concave portions 56a, 56b respectively have a guide groove 57 for a shutter 60 (described later).
The cartridge further includes the shutter 60 consisting of three sheets (two of the sheets facing each other) for opening or closing the center holes 54a, 54b and the head slits 55a, 55b. The shutter 60 is provided with projections 61 and clicks 62. The projections 61 are inserted in the guide groove 57 of the concave portions 56a, 56b. Because of this structure, the shutter 60 is held in the concave portions 56a, 56b so as to sandwich the upper half 53a and the lower half 53b. The shutter 60 is movable in directions indicated by arrows K and L. The clicks 62 can be inserted in a slit 58 formed in the case where the upper half 53a is placed on the lower half 53b.
As shown in FIG. 15, a guide groove 66 is formed on one side of the cartridge box 52 in the vicinity of the head slits 55a, 55b. The guide groove 66 is curved so as to have a bend angle of 90 degrees and is connected to an opening groove 59 formed on an outside face of the cartridge box 52 (see FIG. 14). In the guide groove 66, a flexible slider 63 is movably held. The slider 63 has engaging holes 64 into which the clicks 62 of the shutter 60 are inserted. Thus, the shutter 60 is fixed to the cartridge box 52 via the slider 63. The slider 63 has a projection 65 on the side of the opening groove 59 of the cartridge box 52. The projection 65 engages the shutter opener of a cartridge holder in a drive device to allow the slider 63 to move.
A tension coiled spring 67 is stretchably provided in a space between the slider 63 and a disk housing 68 of the cartridge box 52. One end of the tension coiled spring 67 is fixed to the center of the slider 63 and the other end thereof is fixed to the lower half 53b. Because of this structure, the tension coiled spring 67 is pulled in a direction indicated by the arrow L so that the shutter 60 covers the center holes 54a, 54b and head slits 55a, 55b. When the shutter opener is inserted in the opening groove 59, the projection 65 comes into contact with the shutter opener, and the shutter 60 moves in the direction indicated by the arrow K so that the center holes 54a, 54b of the shutter 60 and the head slits 55a, 55b are opened.
Hereinafter, the construction of the cartridge will be described.
A disk 51 is placed in the disk housing 68 of the lower half 53b and the slider 63 is inserted into the guide groove 66. Thereafter, one end of the tension coiled spring 67 is fixed to the center of the slider 63 and the other end thereof is fixed to the lower half 53b. Under this condition, the upper half 53a is placed on the lower half 53b, and these halves 53a, 53b are fixed with screws and the like. Then, the shutter 60 is provided to the slider 63 so as to sandwich the concave portions 56a, 56b to complete a cartridge.
Next, another conventional example of a cartridge in accordance with International Standards for a 90 mm optical disk will be described with reference to FIG. 16.
A slider 72 is provided in a cartridge box 71. A shutter 73 is slidable along the slider 72. The cartridge box 71 has an opening 74 on its front face, through which a twisted coiled spring 75 can be inserted. One end of the twisted coiled spring 75 is fixed to the cartridge box 71 and the other end of the twisted coiled spring 75 is fixed to the slider 72, whereby the twisted coiled spring 75 pushes the slider 72.
The above-mentioned first example of the conventional cartridge has the following problems:
(1) It is difficult to construct the cartridge: When the cartridge is constructed, the upper half 53a should be placed on the lower half 53b under the condition that the tension coiled spring 67 is stretched (i.e., the tension coiled spring 67 pulls the slider 63 in the direction indicated by the arrow L). Under this condition, the slider 63 is likely to come out of the lower half 53b, since the slider 63 is guided only by the guide groove 66 of the lower half 53b. For example, in the case where slight shock is applied to the lower half 53b at a time when the upper half 53a is placed on the lower half 53b, the slider 63 and the tension coiled spring 67 Jump out of the lower half 53b.
(2) The tension coiled spring 67 or the slider 63 may jump out of the lower half 53b, bump against the disk 51 stored in the lower half 53b, and cause damage to the disk 51.
(3) The structure of this cartridge is unsuitable for miniaturizing the cartridge. That is, this structure requires a space for the movement of the tension coiled spring 67 in the cartridge box 52, resulting in the large depth for the cartridge.
As for the second example of the conventional cartridge, it is relatively easy to construct the cartridge. However, the opening 74 is not closed after the completion of the cartridge; therefore, there is a possibility that dust or the like enters the cartridge box 71 to cause difficulties in opening or closing the shutter 73. In addition, the twisted coiled spring 75 can be caught from outside of the cartridge box 71, so that the twisted coiled spring 75 is easily removed causing damage to the function of the cartridge.